A General Review of Applied Grapevine Nutrition Principles

On June 10, 2020, Dr. Tony Wolf presented Assessing and Managing Vine Nutrient Status in Mature Vineyards as part of the Penn State Wine and Grape Team's weekly webinar series. Tony discussed perspectives on why vineyard nutrition is important, how vineyard nutrition can be assessed, ways to optimize vine nutrient status. Tony reviewed nitrogen management considerations in vineyards that maintain cover crops on the entire vineyard floor and also discussed the popular topic of potassium nutrition (as it relates to wine pH issues). What follows is a brief review of the points discussed. Use this blog post, the information in Tony's slides, and the Wine Grape Production Guide for Eastern North America as information resources to guide nutrient management in your own vineyard.

Assessing vine nutrient status

Soil tests reveal mineral nutrients status of the soil, which may be available for vine uptake. Plant tissue tests reveal mineral nutrient status of the vines themselves and are indicative of the mineral nutrients that are or are not, effectively taken up from the soil. While plant tissue analysis is most revealing of actual vine nutrient status, both soil and plant tissue tests are important to assess in order to understand and effectively manage vineyard nutrition. Visual observations can also be used to help diagnose mineral nutrient imbalances; however, plant tissue tests should be used to objectively confirm those visual diagnoses. As an extension publication from Rutgers points out, leaf reddening can be caused by numerous issues, including nutrient imbalance or systemic infections. Note that it is not uncommon for young vines to display foliar mineral nutrient deficiency symptoms as their root systems are shallow and small and are thus ineffective at accessing some of the soil nutrients, particularly during drought conditions. Similarly, foliar mineral nutrient deficiency symptoms may also be more common in vines planted on vineyard sections with "lean, rocky soils" (e.g. on highly sloped hillsides, or at the apex of a convex landform). 

The two common growth stages to sample grapevine tissues for nutrient analyses are at bloom and "mid-summer," or veraison. Assessment of vine nutrient status is timely right now as many PA vineyards are at bloom, or will be at bloom, in the near future. It is important to notify the analytical laboratory about the stage at which tissues were sampled as tissue nutrient concentrations change over the course of the season. For example, petioles at bloom generally contain greater nitrogen concentration compared to petioles at veraison.

Petioles (leaf stems), leaf blades (lamina), or whole leaves (petioles + blades) are all examples of grapevines tissues that can be sampled and submitted for mineral nutrient analysis. It is thus also important to notify the analytical laboratory about the specific tissues (e.g. petioles, blades, whole leaves) being submitted as sufficiency ranges vary between tissues. Historically, petioles have been the most common grapevine tissue used for nutrient analyses in the United States; thus, interpretation of petiole analyses are based on a comparatively larger database relative to leaf blades or whole leaves (petioles + blades). There are several analytical laboratories that will quantify tissue mineral nutrient contents, including the Penn State Agricultural Analytical Services Lab. 

Correcting vineyard nutrient imbalances

Optimal soil pH for grapevines ranges from 5.5 to 6.5, which corresponds to the soil pH at which many soil macronutrients and micronutrients are available for plant uptake. Correction of soil pH is more effective before planting, when amendments such as lime can be disked and incorporated into the soil. After a vineyard is established, several commercial fertilizers, lime, and other amendments are available to correct grapevine nutrient imbalances. Soil mineral nutrient analysis, grapevine tissue mineral nutrient analysis, soil type, and vine age should all be taken into consideration when developing a plan to correct vineyard nutrient imbalances.

Nitrogen and under-trellis cover crops

The use of cover crops and grasses in vineyard alleyways is a common practice in order to prevent soil erosion and accommodate tractor and ATV traffic. However, more recently, growing cover crops underneath the vine trellis is becoming common in an attempt to combat vine vigor in humid regions that promote vine vigor through supra optimal water and nutrient availability. Further, as vineyards are established on steeply sloped sites (15 to 20%), under-trellis cover crops provide a means to prevent soil erosion on these particularly prone sites. One potential drawback to under-trellis cover crops is their competition with vines for available nitrogen, and potentially other soil mineral nutrients. Too much resource competition could result in greater vigor reduction than desired, which could ultimately result in poor perennial vine health, decreased crop yields, and premature vine decline. To be brief, the importance of monitoring vine nutrition may be heightened when under-trellis cover crops are used; while nitrogen may be particularly important to monitor, cover crops may also compete with other essential mineral nutrients such as phosphorus. Find more details on cover crops and nitrogen nutrition in Tony's slides.

Potassium and wine pH

With some exceptions (e.g. young vineyards, high pH soils), soil potassium is generally in sufficient quantities and readily available for uptake in eastern US vineyards. Potassium is an important macronutrient and is needed for many physiological and metabolic processes in plants. Thus, potassium deficiency should be avoided. Potassium has a (somewhat weak) positive correlation to grape, must, and wine pH. Due to potential drawbacks of high wine pH (color and microbial instability), excessive vine potassium concentration is undesirable. Limited management tools are available to moderate potassium uptake. However, using rootstocks with V. berlandieri heritage (e.g. 420-A, 100-R), limiting canopy self-shading, and avoiding planting on sites with excessive soil potassium are a few ways to limit potassium concentrations in vine tissues, including harvested grapes. See Tony's slides (below) for more detail on potassium nutrition. Also, see previous outreach literature on potassium nutrition from Tony Wolf and Michela Centinari. 

For More information

Tony Wolf's Presentation slides: Assessing and managing vine nutrient status in mature vineyards